(a) Field of the Invention
The present invention relates to a sample tray feeding apparatus be used with automatic electrophoresis apparatus or a similar analytical instrument, and more specifically to a sample tray feeding apparatus so adapted as to prevent samples from being dried.
(b) Description of the Prior Art
There have conventionally been known apparatus which automate in electrophoresis the individual steps such as application of sera onto a carrier made of cellulose acetate paper or the like and forming fractionated patterns through electrical energizing. Among these apparatus, the automatic serum applying apparatus uses an applicator having a large number of blades which are to be inserted into sample trays filled with samples, for example, sera for allowing them to adhere to said blades and then lowered onto a carrier for applying said samples onto said carrier. After the application of the samples, the applicator is shifted into a washing tank for washing off the sera remaining on the blades with washing water and then the washing water adhering onto the blades is removed through drying or by wiped off with filter paper. At the subsequent stages, the above-mentioned steps are repeated for applying other samples successively.
The automatic serum applying apparatus described above uses sample trays (serum trays) having such a construction as shown in FIG. 1. Speaking concretely, the sample tray 1 has an elongated form with numerous cavities 1a formed therein to be filled with samples 2. The samples are successively fed to the adhering position on the applying device by a sample tray feeding apparatus 3 such as shown in FIG. 3. This sample tray feeding apparatus consists of a shifting table 4 having a positioning pin 4a, and functions to set the sample tray 1 at a predetermined position on the shifting table 4 with the pin 4a, shift the table 4 in the direction indicated by the arrow C in FIG. 2 and shift the sample trays consecutively to the adhering position A. Speaking more concretely, a first sample tray 1 located on the left side end in FIG. 2 is shifted first to the position A, applicator 5 having such a construction as shown in FIG. 3 of the serum applying device is brought over the position A and lowered down into the sample tray 1, whereby the blades 5a are dipped into the samples placed in the sample tray 1. The samples are allowed to adhere to the tips of the blades 5a. The blades 5 a are thereafter lifted up, shifted in the direction indicated by the arrow D (from the right to the left in the drawing) and then stopped at the applying position B. At this position, the applicator 5 is lowered down to apply the samples onto a carrier 7. After the application of the samples, the carrier is sent to the next stage by an adequate conveying means for forming fractionated patterns of the samples. The applicator is lifted upward and then shifted horizontally to be passed consecutively through a washing tank and drying device (not shown) for washing and drying the blades. The applicator 5 is thereafter shifted rightward to be returned to the position A.
During the step to return the applicator to the position A as described above after the washing and drying, the shifting table 4 of the sample feeding apparatus 3 is shifted leftward in the drawing and the next sample tray is set at the position A. At each of the steps from the sample adhering to blade drying by applying device, the sample trays are consecutively fed to the adhering position by shifting the sample tray feeding apparatus at definite intervals. In the conventional sample feeding apparatus operating as described above, water content is vaporized from the samples for the standby time required after samples are set in the sample feeding apparatus until samples are allowed to adhere to the blades. Since a long time is required from application of a sample onto a carrier to the formation of electrophoretic patterns, a long time must be reserved between adhesion of samples to a blades and that of the next samples. Therefore, the next samples are condensed due to vaporization of water contents from said samples during the standby time. When a sample which is condensed as described above is applied onto a carrier, non-uniformity or disturbance of the application causes adverse effect on analytical result. Vaporization of water content is more remarkable and causes more seriously adverse effect especially on analytical results of samples which are set in later sample trays and require longer standby times.